Alloy steel



Columbia, useful Improvements in Alloy Steel; and I to shock and strain or in other situations UNITED STATES PATENT OFFICE.

PHILIP M. MGKENNA, OF CONGRESS HEIGHTS, ISISTRICT OF COLUMBIA.

ALLOY sr'nnn 80 Drawing.

To allwkom it may concern:

Be it known that I, PHILIP M. Mo- KENNA, a citizen of the United States, residing at Go ress Heights, in the District of ave invented certain new and do hereby declare the following to be a full, clear, and exact description of the same.

This invention relates to the steel industry and more especially to that branch of the industry having to do with alloy steels, the objects of the invention being to produce an alloy steel which is tough and strong and possesses an evenness of grain which makes it valuable for use in machine parts subject where .a uniformly strong metal is desired, as, for example, in springs, gun barrels, saws, etc.

The invention consists in an alloy steel which besides iron contains carbon, chromium and tantalum as the characteristic imparting elements,'although there may be present, incidentally, impurities in negligible quantity, such as sulfur, phosphorus, silicon, manganese, columbium, vanadium, etc.

The alloy of the present invention contains not less than .20 per cent. of carbon, preferably carbon .20 to .50 per cent., chromium .70 to 1.60 per cent., and tantalum 1 to 3 per cent. .with the remainder iron, save for the impurities resent in the ingredients and which it is iflicult to entirely eliminate.

. The alloy may be readily produced in electrio or in other suitable steel melting furnaces. If it is produced in theopen-hearth furnace the ferro-tantalum should be added Patented Sept. 6, 1921.

1921. Serial No. 458,032.

exist in the right proportions with the exception of the ferro-tantalum. Then the ferro-tantalum is added to the ladle.

The ferro-tantalum may be produced by reducing tantalite or columbite with iron oxid, in an electric furnace, or by alumino thermic reaction. This will result in a ferro alloy containing about 30 per cent. tantalum. It is very essential to use only tantalite -or columbite ore which is free from deleterious impurities such as tin, antimony, copper, sulfur, arsenic and phosphorus which otherwise go into the alloy and cause the metal to be subject to breakage, and lose its valuable physical properties. The ferro-alloy is added to the molten bath in pieces about the size of peas, in order that the metal may readily absorb the ferro-tantalum.

The metal produced can be worked up into 

